Central Carbon Metabolism

Central Carbon Metabolism • In recent year, it is of keen interest to investigate the relationship between the structure and function of microbial metabolic networks in systems biology. Central carbon metabolism plays an important role in metabolic network and is composed of the flow of carbon from nutrients into biomass. With the assistance of advanced analytical technologies and decades of painstaking efforts, the structures and functions of the pathways for the carbon flux has been significantly clarified. In the classic textbook, the central carbon metabolism is defined as composed of the glycolysis pathway, the citric acid cycle, the pentose phosphate pathway, six known carbon fixation pathways and some pathways of methane metabolism, though the definition of this metabolism is remains to be validated with experiments.

• This definition comes into being because of the comprehensive investigations with carbohydrates and extensive experimental elucidation of the structure of the central carbon metabolism and the metabolic network. There are minor variations depending on the ecological niche the organism lives. In some species such as saccharolytic archaea, modified nonphosphorylated ED pathways is known to take the place of the conventional EMP pathway. • The six carbon fixation pathways are as below. (1) Reductive pentose phosphate cycle (calvin cycle) in plants and cyanobacteria taking part in oxygenic photosynthesis. (2) Reductive citrate cycle exist in photosynthetic green sulfur bacteria and some chemolithoautotrophs. (3) 3- hydroxypropionate bi-cycle found in photosynthetic green nonsulfur bacteria. (4) Hydroxypropionate-hydroxybutyrate cycle in Crenarchaeota. (5) Dicarboxylate-hydroxybutyrate cycle also in Crenarchaeota. And (6) reductive acetyl-CoA pathway occurs in methanogenic bacteria.

• ith the assistance of a complex series of enzymes, central carbon metabolism converts sugars into precursors for metabolism, which are used to produce the entire biomass of the cell. The structure of central carbon metabolism follows the optimality principle. It is found that central carbon metabolism is a minimal walk between the 12 precursor metabolites essential for biomass and one precursor needed for the ATP balance in glycolysis. Each pair of consecutive precursors in the central carbon metabolism network is linked by shortest enzymatic reactions. At the same time, input sugars converts precursors with the minimal number of possible enzymatic paths. • LC–MS/MS platform enable simultaneous relative and absolute quantification of multiple metabolites in a biological system. The results are widely used for biomarker discovery by investigating the relative changes in metabolite concentrations. The resulting data have been widely used to for biomarker discovery. By providing the exact molecular weights and retention time, LC–MS/MS techniques serves as a powerful analytical tool for identification and quantification of small molecules (metabolites). Creative Proteomics has established sensitive, reliable, and accurate HPLC-MS/MS method for quantification of metabolites in central carbon metabolism pathway.